add fake HTTP HEAD checking for google code URLs

this allows google code urls to pass link checking.

refs #131

lib/cask/fetcher.rb

@@ -1,5 +1,21 @@
+require 'open3'
+
 class Cask::Fetcher
+  TIMEOUT = 10
+
   def self.head(url)
-    `curl --max-time 5 --silent --location --head '#{url}'`
+    if url.to_s =~ /googlecode/
+      googlecode_fake_head(url)
+    else
+      `curl --max-time #{TIMEOUT} --silent --location --head '#{url}'`
+    end
+  end
+
+  # google code does not properly respond to HTTP HEAD requests, like a jerk
+  # this fakes a HEAD by doing a GET, taking the first 20 lines, then running away
+  def self.googlecode_fake_head(url)
+    command = "curl --max-time #{TIMEOUT} --verbose --location '#{url}' | head -n 20 > /dev/null"
+    stderr = Open3.popen3(command) { |_, _, err, _| err.read }
+    stderr.split("\n").grep(/^< /).map { |line| line.sub(/^< /, '') }.join("\n")
   end
 end